In specific circumstances electronic devices need to be galvanically isolated from one another while still being in operative communication. For example, devices that need to be communicatively coupled to exchange information while at the same time operating in different power regimes may need to be isolated so that the lower power device is not damaged by exposure to current levels that it cannot withstand. As another example, a peripheral device operating with a power supply having a first ground level, such as the negative terminal of a battery, may need to communicate with a host device operating with a separate ground level, such as the ground terminal of a mains wall socket. In these circumstances, isolation is required to prevent current flowing from one “ground” to the other when the devices are coupled together. As another example, isolation can protect a device from being adversely affected by fault conditions in a separate device. In all of these circumstances, the devices may be galvanically isolated while still being in communication via electrical, optical, mechanical, or acoustic means.
One of the main considerations that must be taken into account when designing an isolator is the ability of the isolator to withstand large power levels while maintaining a desired degree of isolation. Traditional isolators have therefore utilized a split paddle assembly process in which each side of the isolator is supported by an entirely separate substrate. The two separate substrates are in turn bound together through a packaging process to an overall lead frame that will generally also support contacts to the overall circuit. The isolation device itself is formed between the separate paddles and provides a communication channel between the two while maintaining their galvanic isolation.
FIG. 1 illustrates another approach to enhance the power hold-off capability of an isolator which is to form the isolation devices themselves in the substrate to which the isolated devices are connected. FIG. 1 illustrates isolator assembly 100 that comprises substrate 101 in which two capacitors 102 have been formed via a dielectric layer 103 and conductive traces 104. Separate isolated devices 105 can be connected to the conductive traces at locations 106 and 107 and are thereby isolated via the two capacitors 102. Since the isolation device is formed in the substrate and the breakdown voltage of dielectric 103 is much larger than air, the hold-off voltage capability of the isolator is commensurately increased. Separate devices 105 can include transceiver circuits for encoding signals to be sent through the capacitors 102 and can connect to external isolated circuits via conductive traces 108.